I recently launched a new site using this wonderful product known as Zen Cart. It was working as planned until recently when a customer said they couldn't find one of the products. Sure enough some pages come up blank (without any listing) and on others the first page of the listing shows while the "next" page is empty.

Here's an example:
http://www.china-bazaar.com/ click on Knives > Folding. You'll see the first page with items 1-10 of 31. Click on the "next" page (or page 2) and there's nothing.

Some of the other categories exhibit this problem on the first page of the listing (they have less than 10 items). Axes is an example of this (five items in the database).

I have this site working properly on my local server. It was working remotely on the hosted site until recently.

Any ideas on what may be causing this??

TIA